Method for the production of cellulose acetate cigarette filter tips



Jam 30 1968 w. R. MAHoNEY ETAL 3,366,521

METHOD FOR THE PRODUCTION OF CELLULOSE V ACETATE CIGARETTE FILTER TIPSOriginal Filed July 19, 1960 Curl-Ef 1N V EN TRS Jsebh L Baruchl willie,R. Ma bn WAX Arrow/frs United States Patent Gflce 3,365,5Zl PatentedJan. 30, 1968 3,366,521 METHOD FOR THE PRGDUCTION F CEL- LULOSE ACETATECIGARETTE FILTER TIPS William R. Mahoney, Gulf Breeze, Fla., and JosephL.

Barach, Charlotte, N.C., assignors to Celanese Corporation, acorporation of Delaware Continuation of abandoned application Ser'. l\lo. 346,288, Feb. 26, 1964, which is a division of applicatlon Ser. No.43,863, July 19, 1960. This application Jan. 30, 1967, ser. No. 612,733

v 4 Claims. (Cl. IE6-62.2)

ABSTRACT 0F THE DSCLGSURE Method for the production of cellulose acetateflake cigarette filter tips employing flake having a particle size ofabout 5 to 20 mesh, a substantial proportion of the particles having aparticle size of about 5 to 10 mesh; and a lbulk density of less thanabout pounds per cublc foot.

The present application is a continuation of application Ser. No.346,288 led Feb. 20, 1964, now abandoned, which is a division ofapplication Ser. No. 43,863 filed luly 19, 1960, now U.S. Patent3,126,009, which in turn is a continuation-in-part 0f application Ser.No. 640,667 filed Feb. 18, 1959, now abandoned.

This invention relates to the production of cigarette filter tips fromcellulose esters, such as cellulose acetate.

'It has previously 'been proposed that cigarette filter tips be preparedfrom spun cellulose acetate filamentary material. In one commonly usedprocess a continuous bundle of continuous filaments of celluloseacetate, said bundle being known as tow, is fed to the wrapping sectionof a cigarette-making machine, where it is enclosed in a paper wrapper.The resulting wrapped tow is then cut to short lengths suitable for useas cigarette filter tips. This process has several disadvantages. Forexample, there is a considerable tendency for the continuous tow tospring out of its wrapper before the cutting operation; this results injamming of the machine. Furthermore, the filter tips produced by thisprocess are unduly expensive. In addition such tips do not have as higha ltenng power as desired.

It is therefore an object of this invention to provide a process formaking a novel cigarette filter tip, which Will be free from theforegoing defects.

A further object of this invention is the provision of a new process formaking a new cigarette filter tip made made from cellulose ester flakematerial.

Other objects of this invention will be apparent from the followingdetailed description and claims. In this description and claims allproportions are by weight unless otherwise indicated.

The cigarette filter tips of this invention are made from finely dividedcellulose ester material. Preferably the finely divided cellulose estermaterial used is that known in the industry as ilake, prepared byprecipitating the cellulose ester in the form of fibrous or hairy porousparticles from a solution of said cellulose ester in a solvent. Inaccordance with one aspect of the invention, the loose cellulose esterflake material is enclosed in a wrapping to form a rodlike wrappedstructure containing the discrete particles of said flake material.Thereafter, this wrapped structure is treated to cause the discreteparticles to cohere at randomly spaced points of contact and is cut tothe length of the desired filter tip.

The cellulose ester flake material of this invent1on 1s preferably madeof cellulose acetate, although other cellulose esters such as thepropionate, ybutyrate, acetate-propionate or acetate-butyrate may 'beemployed in place of the acetate or in ad-mixture therewith. While thecellulose acetate may be of any desired type, e.g. cellulose triacetate,best results have been obtained with acetonesoluble secondary celluloseacetate having an acetyl content of about 50 to 56% by `weightcalculated as combined acetic acid. When the acetyl value ranges fromabout 52 to 55% and preferably about 53% the flake comprises long,strong, soft hairy fibers of excellent filtration characteristics. Theprecipitation of the cellulose ester to form the flake may be effectedin known manner; for example by adding dilute acetic acid to a solutionof the cellulose acetate in glacial acetic acid and thoroughly agitatingso as to produce a porous fibrous flake, and then washing. Examples ofmethods for forming such a flake are found in U.S. Patent No. 2,010,111,as well as in U.S. Patent No. 2,740,776, and in the prior art discussedtherein. Flake screened to a particle size in the range of about 5 to 20mesh has given very good results. Preferably at least half the flake hasa particle size in the range of about 5 to 10 mesh. Advantageously thebulk density of the flake is less than about 20 pounds per cubic footand preferably about 15 pounds or less per cubic foot as contrasted witha density of more than pounds per cubic foot for solid secondarycellulose acetate. In addition t0 the decreased weight and thus cost perfilter, the low density flake affords a large surface for improvedfiltration While permitting easy drawing of smoke therethrough. In ahighly effective preferred embodiment of this invention the cohering ofthe particles of flake, after Wrapping, is effected vby the applicationof heat so as to sinter said particles together. When this embodiment ofthe invention is employed it is found most advantageous to apply asuitable plasticizer to the flake in order to reduce the softeningtemperature of the surfaces of the particles. The plasticizer should besubstantially non-volatile at room temperature and is preferablysubstantially odorless, colorless, tasteless and non-toxic. Examples ofsuitable plasticizers of this type are di-lower alkoxy-lower alkylphthalates such as di-methoxyethyl phthalate, dialkyl phthalates such asdiethyl phthalate, dioctyl phthalate 0r diisooctyl phthalate, loweralkyl phthalyl lower alkyl glycolates such as methyl phthalyl ethylglycolate, ethyl, phthalyl ethyl glycolate or butyl phthalyl butylglycolate, tri-lower alkyl citrates and acylated derivatives thereofsuch as tri-ethyl citrate, acetyl triethyl citrate, or acetyl tributylcitrate, di-alkyl sebacates such as dibutyl sebacate, triacetin, andblends of the foregoing plasticizers with each other or with otherplasticizers, such as blends of triacetin and mono-octyl diphenylphosphate. The plasticizer may be applied conveniently by spraying itonto the flake. To insure even distribution of plasticizer the particlesof the flake may be tumbled or otherwise agitated during and/or afterthe application of the plasticizer thereto. Another method of applyingthe plasticizer is by immersing the particles in a bath containing theplasticizer. For example, the flake may be immersed in and thenwithdrawn from a s0- lution of the plasticizer in a volatile non-solventfor the cellulose ester, or an aqueous emulsion of the plasticizer;

in this case the water or other non-solvent is preferably evaporatedbefore the tiake material is wrapped. The amount of plasticizer appliedmay :be varied depending on the particular plasticizer and theparticular cellulose ester chosen; one suitable range is 5% to 30% ofplasticizer based on the weight of the cellulose ester.

The wrapping of the ilake material may be carried out on the usualcigarette making machinery. Thus the ake material may be fed in acontinuous stream onto a belt or series of belts where the fiakematerial is compacted, and then brought into contact with a continuousstrip of cigarette paper in precisely the same way as the t0- 'baccoparticles are fed, compacted and brought into contact with the paper ona cigarette-making machine, such as that described in U.S. Patents Nos.2,283,394, 2,247,- 413 or 2,208,504. The paper and the flake materialmay be brought into contact with a shaping element which bends the sidesof the strip of paper around the ake material, after which the parallellongitudinal edges of the paper strip are sealed, as by gluing, to forma continuous wrapped rod. As is common in the cigarette making art,during this operation one side of the paper strip, opposite the side onwhich the particles being wrapped are resting, is maintained in contactwith a supporting wrapping tape, belt or other forming element, such asis shown in US. Patents Nos. 2,208,504 and 2,247,413, mentioned above.After the wrapping operation this forming element is removed fromcontact with the paper. The wrapped rod has approximately the samecross-sectional coniiguration as the usual cigarette, i.e. it is roughlya cylinder about 25 to 27 mm. in circumference but this may be alteredas required.

In the preferred embodiment of this invention the wrapped rod containingthe discrete particles of flake material is baked to cause the sinteringof the particles at random points of contact. The temperature and timeof baking may be varied, depending on the type of cellulose esterparticles and amount and character of plasticizer. Baking in a hot airoven at 170 C. for an hour has given good results with secondarycellulose acetate ake plasticized with approximately of triethylcitrate. At lower temperatures, e.g. l40-150 C., longer times, generallytwo hours or more, are satisfactory. Instead of hot air, other heatingmedia may -be employed. When the plasticizer is one which is more activeat room temperature, e.g. triacetin, the baking operation may beeliminated, since the same effect is obtained by allowing the wrappedmaterial, containing, for example about 20% of plasticizer, to stand forsome time, e.g. 2 hours, at room temperature. In either case theresulting wrapped rod comprising the cohering particles of celluloseester may then be incorporated into a cigarette in a mannerconventionally employed for making cigarette filter tips. Thus thewrapped rod, which may have been cut into intermediate lengths beforethe particles were bonded together, may be cut into lengths suitable forindividual filter tips, e.g. 11 to 15 mm. lengths, and Wrapped incigarette paper together with the tobacco to form a cigarette. Thewrapped rod may also be cut to twice iilter-tip length and incorporatedin cigarette paper with suitable lengths of tobacco at each end, inaccordance with methods well known in the cigarette art, after which theresulting structure may 4be cut transversely through the middle of thedouble length of filter to form two tilter-tip cigarettes.

If desired, the original wrapper may be removed from the rod of coheringparticles of cellulose ester before the final wrapping -of the rod andtobacco to form the cigarette. For example, paper need not be used forthe initial Wrapping of the discrete cellulose ester particles. Instead,these particles may be wrapped in another sheet material. 'Ihus they maybe wrapped merely in a supporting Wrapping tape or belt, such as thatreferred to above, and treated to cause the particles to cohere while soWrapped, after which the supporting wrapping belt may be unwrapped orotherwise removed, leavin-g a self-supporting porous rod of coheringparticles, which rod may be cut and incorporated into a cigarette as thelter tip thereof. In either case the forming of the flake into coherentrod form takes place without substantial relative longitudinal movementof wrapping material and flake.

The lter tips of this invention are highly effective for the removal oftars and other undesirable substances from tobacco smoke. In contrast tolter tips made in the usual manner, from cellulose acetate tow, theyproduce a more turbulent, rather than laminar, ovv of the smoke withoutsubstantial effect on the ease of drawing the smoke through the filter.In addition, they can be manufactured at lower cost, using standardcigarettemaking machinery if desired.

In the drawing, which illustrates the process and product of thisinvention, as well as the flake used,

FIG. 1 is a iiow diagram of the process of making the filter tip,

FIG. 2 shows the cigarette embodying the iilter tip of this invention,

FIG. 3 is an enlarged View of individual particles of a celluloseacetate ake suitable for use in this invention, and

FIG. 4 is an enlarged cross-sectional view, taken through the filtertip, along the line 4 4 of FIG. 3.

In FIGS. 2 and 4 of the drawing, reference numeral 11 designates thesintered iiake particles of the lter tip 12, enclosed within a cigarettepaper wrapper 13 and positioned at one end of the cigarette 14.

The following examples are given to illustrate this invention further.

Example I Flake of fibrous porous particles of cellulose acetate of54.5% acetyl content, calculated as acetic acid, is passed through a No.5 mesh screen (4 mm. openings) and then a No. 20 mesh screen (0.84 mm.openings). The flake retained on the No. 20 mesh screen is tumbled in arotating vessel while triethyl citrate, a non-toxic plasticizer, issprayed intermittently into the vessel, the total amount of triethylcitrate being 1/s the weight of` cellulose acetate. The appearance ofthe ake after the application of the plasticizer is substantiallyunchanged. The material is then fed to a standard cigarette-makingmachine Where it is compacted and wrapped in standard thin cigarettepaper to form a generally circular rod having a circumference of 27millimeters weighing 181/2 grams per meter, of Which 0.7 gram is theweight of the paper, with the edges of the paper overlapped and gluedtogether. The Wrapped material isplacedin a hot air oven where it isbaked at C. for 60 minutes. After cooling, the baked material is cutinto 15 mm. lengths and incorporated as the filter-tip in a cigarette 70mm. in length. This cigarette when smoked draws easily and filters thesmoke eiciently. The iilter tip, though highly porous, does not break orcrumble on handling, even after the paper is removed.

Example II Example I is repeated, substituting dimethoxyethyl phthalatefor' the triethyl citrate, with similar results.

Example III If Example I is repeated employing cellulose acetate flakeof 53% acetyl value and having a bulk -density of v particles ofcellulose acetate fibrous ake having an acetyl value in excess of about52% by weight calculated as combined acetic acid, having a bulk densityless than about 20 pounds per cubic foot and a particle size of about 5to 20 mesh, a substantial proportion of the particles having a particlesize of about 5 to 10 mesh bringing a mass of discrete particles of saidake into contact with a sheet material, Wrapping said sheet materialaround said brous flake to form a cylindrical rod cornprising saiddiscrete particles pressed together Within said sheet material, andheating to elfect bonding of said particles together at points ofcontact.

2. Process as set forth in claim 1 in which said rod is cut into alength of about 11 to 15 mm. for use as a cigarette lter.

3. Process as set forth in claim 1 in which said plasticizer is selectedfrom the group consisting of triethyl citrate, methyl phthalyl ethylglycolate, dimethoxyethyl phthalate, and triacetin.

4. Process as set forth in claim 3 in which the proportion ofplasticizer is about 5 to 30%, based on the Weight of cellulose acetate.

References Cited UNITED STATES PATENTS 2,794,239 6/ 1957 Crawford et al131-208 2,805,671 9/1957 Hackney et al. 131-208 2,828,752 4/ 1958Jackson 131-208 2,979,058 4/ 1961 Schur 131-94 X 3,201,505 8/1965 Meyer131-10 X FOREIGN PATENTS 757,841 9/ 1956 Great Britain.

SAMUEL KOREN, Prima/'y Examiner.

MELVIN D. REIN, Examiner.

